The Acoustics of Voicing: Analyzing the Spectral Effects of the Voicing Process

Part 3: Voicing Up

By Jason Cassel

Peppering the Crown

In Part 2 of this series, we considered techniques commonly used to increase power and dynamic range in both hard-pressed and soft-pressed hammers. In this article, we will examine common methods for “voicing down,” or decreasing the presence of a note that might stick out when compared to its neighbors. In his book Under the Lid, Stephen Brady explains, “As in action regulation, evenness in tone regulation is critical if the pianist is to have complete control of the instrument. The tone must be absolutely even from one note to the next.”

For both hard-pressed and soft-pressed hammers, this process is usually accomplished by identifying notes that stick out from others, and applying shallow needling in or near the crown, or in some cases, into the strike point. 

The first of these approaches we will consider is often referred to as “peppering the crown.” This is done by taking a shallow single needle and quickly tapping the needle around the crown of the hammer (see Photo 1).

Where to pepper the crown.

Graph 1 shows the tonal spectrum of F4 played by a soft-pressed hammer before and after peppering the crown. Remember that the x-axis shows the partial number and the y-axis shows the volume of each partial at that moment. The blue line represents the tone before needling. The orange line represents the tone after needling. With this in mind, examine Graph 1 and notice how there is a decrease in the amplitude of higher partials with minimal effect made to the core or power of the tone built in the lower partials. This is demonstrated aurally in Video 1. It is also worth noting that a similar pattern was seen in the hard-pressed hammer as well. 

Graph 1: Peppering the crown, before and after (soft-pressed hammer).

One common criticism of “peppering the crown” is that its effect is considered temporary. While I did not attempt to quantify how long these changes in partial amplitudes remained present, it is clear that “peppering the crown” does effectively alter the tonal spectrum for a given note – even if those changes are temporary. 

Needling Under the Crown 

Perhaps the most common technique used in voicing down a note is shallow needling under the crown. This is often performed by inserting a chopstick needling tool at the edge of each string groove (see Photo 2). During a final voicing, it is often best to listen to each string individually to determine which of the three strings is most offensive – then needle only at the edge of that string’s groove. In this study, however, the edge of all three string grooves were needled. 

Where to needle under the crown.

Graph 2 shows the tonal spectrum for F4 played by a soft-pressed hammer before and after needling. Once again, much of the core and power of the tone provided in the lower partials remained unchanged, while the amplitudes of the middle and higher partials were decreased – as demonstrated in Video 2.

Graph 2: Needling under the crown, before and after (soft pressed hammer).

The Steinway World-Wide Technical Reference Guide explains the results of Graph 2 further, stating, “As power is built, so is noise, i.e. a disproportionate distribution of energy to the upper partials. The reduction of noise is accomplished… [by] listening to individual strings and using a single needle precisely at the point of contact with that string, you will retain the power of the note and reduce noise” (emphasis added). In other words, as shown, this technique should lower the amplitudes of the middle (partials 10-20) and higher partials (partials 21+) while leaving the power provided by the lower partials (partials 1-9) relatively unchanged. 

Voicing Down: Needling into the Strike Point 

This technique is a more radical version of the two previous methods. Here, a shallow needle is placed directly downward into the strike point of one or more string grooves. Graph 3 shows the effects of this process on F4 played with a hard-pressed hammer. Again, there is a notable decrease in the middle partials and many of the higher partials – as demonstrated in Video 3. Unlike the previous techniques however, there is also a slight decrease in the power and core provided by the lower partials (partials 1-9). 

Graph 3: Needling into the crown, before and after (hard-pressed hammer).

In summary, Graph 4 shows the effect of all of these “voicing down” techniques on F4 played with a soft-pressed hammer. The color of each line represents the different techniques discussed in this article (see the key on right hand side of the graph). Notice how the amplitudes of the middle and higher partials (partials 10-20 and 20+ respectively) decrease gradually with the application of each technique. Only needling into the strike point (the yellow line) decreases the power and core provided by the first nine partials. Video 4 presents all of these changes. 

Graph 4: Voicing down (soft-pressed hammer).


From Part 3 of this study, we can observe that the presence, color and attack of the tone are established in the middle and higher partials. Additionally, it is clear that in both soft and hard-pressed hammers, the crown and strike point are where the most significant changes to the presence, color and attack of the tone are made. Remember that in Part 2, we observed that the shoulder was where the power and core of the tone were most effected. Thus, generally speaking, lower partials (power and core) are adjusted at the shoulder, and middle partials (presence) and higher partials (color and attack) are adjusted at the crown and strike point. 

In conclusion to this series as a whole, Stephen Brady claims, “The technical skills of tone regulation are relatively easy to acquire; the real difficulty lies in the judgement of when and how to use them.” Similarly, in his book The Voice of the Piano, André Oorebeek confirms, “Determining the course of action in voicing is actually the most difficult task.” As mentioned, voicing is comprised of a variety of factors, which make the process difficult (if not impossible) to measure accurately. Nevertheless, the results of this study prove that there is much to be gained by taking a more analytical approach to a subject that is often veiled in obscurity and generalizations. By more fully understanding what is happening when voicing techniques are employed, piano technicians will be able to better determine when each method should be used. In the end, by anticipating the effect of a given technique and carefully selecting the best course of action, we will be able to more effectively and efficiently meet the demands of the artist by releasing the full potential of the pianos we service. 


Brady, Stephen H. Under the Lid: the Art & Craft of the Concert Piano Technician. 

Seattle: Byzantium Books, 2011.

Oorebeek, André. The Voice of the Piano: A Piano Technicians Definitive Guide to 

Voicing. Nanaimo, BC: Crescendo Publications, 2009.

Steinway & Sons. World-Wide Technical Reference Guide. New York: Steinway & 

Sons, 2017. 

Jason Cassel, RPT, M.A.

Brigham Young University - Salt Lake City, UT

Jason Cassel currently serves as a Piano Technician for the Brigham Young University School of Music. Before accepting this position, Jason Cassel graduated with an MA in Piano Technology from Florida State University – a distinction shared by only a dozen technicians in the nation. He earned his BM in Commercial Music from BYU while working as a student apprentice in the university’s piano shop. Jason has received training at the Steinway & Sons Factory in New York, the Mason & Hamlin Factory in Boston, and from Yamaha Pianos in California.

Jason is a Registered Piano Technician with the Piano Technicians Guild and has presented at local chapter meetings and attended various regional and national conventions. Many of his articles on piano technology have been published in the Piano Technicians Journal and his work on the revolutionary On Pitch DVD Series has been considered “an unprecedented tool to propel the next generation of fine tuners.” (Anne Garee – Former Head of Piano Technology at FSU)


Most of our photography was done by the talented ChiaYu Lee.

 To see more of his series from Heart One Pianos, visit his website. 

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